fix(Cabal): Fix install-includes with a local (relative) path

Cabal/src/Distribution/Simple/Install.hs

@@ -41,7 +41,6 @@ import Distribution.Simple.Compiler
   )
 import Distribution.Simple.Glob (matchDirFileGlob)
 import Distribution.Simple.LocalBuildInfo
-import Distribution.Simple.Setup.Config
 import Distribution.Simple.Setup.Copy
   ( CopyFlags (..)
   )
@@ -347,10 +346,10 @@ installIncludeFiles verbosity libBi lbi buildPref destIncludeDir = do
   let relincdirs = sameDirectory : mapMaybe symbolicPathRelative_maybe (includeDirs libBi)
       incdirs =
         [ root </> getSymbolicPath dir
-        | -- NB: both baseDir and buildPref are already interpreted,
+        | -- NB: both the package root and buildPref are interpreted below,
         -- so we don't need to interpret these paths in the call to findInc.
         dir <- relincdirs
-        , root <- [baseDir lbi, buildPref]
+        , root <- [interpretSymbolicPath (mbWorkDirLBI lbi) sameDirectory, buildPref]
         ]
   incs <- traverse (findInc incdirs . getSymbolicPath) (installIncludes libBi)
   sequence_
@@ -362,7 +361,6 @@ installIncludeFiles verbosity libBi lbi buildPref destIncludeDir = do
           destDir = takeDirectory destFile
     ]
   where
-    baseDir lbi' = packageRoot $ configCommonFlags $ configFlags lbi'
     findInc fs f = go fs
       where
         go [] = dieWithException verbosity $ CantFindIncludeFile f fs

cabal-testsuite/PackageTests/Regression/T11186/cbits/clib.c

@@ -0,0 +1 @@
+int clib(void) { return 1; }

cabal-testsuite/PackageTests/Regression/T11186/cbits/clib.h

@@ -0,0 +1,3 @@
+#ifndef CLIB_H
+#define CLIB_H
+#endif

cabal-testsuite/PackageTests/Regression/T11186/install-includes-local.cabal

@@ -0,0 +1,13 @@
+cabal-version:      2.4
+name:               install-includes-local
+version:            0.1.0.0
+build-type:         Simple
+
+library
+    build-depends:    base
+    hs-source-dirs:   src
+    exposed-modules:  Lib
+    include-dirs:     cbits
+    c-sources:        cbits/clib.c
+    install-includes: cbits/clib.h
+    default-language: Haskell2010

cabal-testsuite/PackageTests/Regression/T11186/setup.cabal.out

@@ -0,0 +1,9 @@
+# Setup configure
+Configuring install-includes-local-0.1.0.0...
+# Setup build
+Preprocessing library for install-includes-local-0.1.0.0...
+Building library for install-includes-local-0.1.0.0...
+# Setup copy
+Installing library in <PATH>
+# Setup register
+Registering library for install-includes-local-0.1.0.0...

cabal-testsuite/PackageTests/Regression/T11186/setup.out

@@ -0,0 +1,9 @@
+# Setup configure
+Configuring install-includes-local-0.1.0.0...
+# Setup build
+Preprocessing library for install-includes-local-0.1.0.0...
+Building library for install-includes-local-0.1.0.0...
+# Setup copy
+Installing library in <PATH>
+# Setup register
+Registering library for install-includes-local-0.1.0.0...

cabal-testsuite/PackageTests/Regression/T11186/setup.test.hs

@@ -0,0 +1,13 @@
+import Test.Cabal.Prelude
+
+-- Regression test for #11186: install-includes should accept a relative
+-- ("local") path and install the header to the include directory.
+main = setupAndCabalTest $ withPackageDb $ do
+  setup_install []
+  env <- getTestEnv
+  shouldExist $
+    testLibInstallDir env
+      </> "install-includes-local-0.1.0.0"
+      </> "include"
+      </> "cbits"
+      </> "clib.h"

cabal-testsuite/PackageTests/Regression/T11186/src/Lib.hs

@@ -0,0 +1 @@
+module Lib where

changelog.d/12257.md

@@ -0,0 +1,13 @@
+---
+synopsis: "Fix `install-includes` with a local (relative) path"
+packages: [Cabal]
+prs: 12257
+issues: 11186
+---
+
+`install-includes` now locates header files relative to the package root (the
+working directory) instead of resolving them through `packageRoot`, which could
+resolve to the directory of the `.cabal` file (a subdirectory of the package
+root when `--cabal-file` is used) or to a raw, uninterpreted `--working-dir`
+path. Previously this could prevent a relative `install-includes` path from
+being found when installing, e.g. from a source tarball.